I just added a radiator and soldered all of the fittings with a resin-core solder. I didnt realize until I was at HD and saw solid solder. Does this matter?

Its holding up fine so far.

 

I honestly don't know. All I have ever used is solid. Maybe one of the other guys will see this & be able to teach us both something.

 

Rosin core solder is meant for electronics work. The rosin is the type of flux that is a sort of catalyst that helps the solder adhere to the copper pipe. The flux chemically cleans the pipe and is a wetting agent to help the solder spread evenly. Applying the flux as you add the solder can result in uneven distribution of solder. My understanding it that the flux itself will cause corrosion at the joint because it is more acidic.
If the system doesn't leak, you may be fine. I have pulled many soldered joints from domestic water systems that were not properly fluxed, with solder not adhereing to the copper on as much as 1/2 of the joint. Yet, they did not leak for years. The pressure in your heating system is much lower than a domestic water system. If you do develop a leak, it will usually be a very slow one, although I have also encountered poorly soldered joints where I could physically knock the pipe out of the joint.
The corrosion factor is not a major problem. The corrosion will be a slow process. Just check the joints from time to time.
If you are a worrywart, it might be worth the time to take those joints apart and resolder them, but that could wait until the summer.
That is the way I see it.

 

I've been reading this group for about 3 days now, trying to absorb all of this stuff. I'm amazed at all the great info. This may be an old thread, but I'd like to put a little something back.

Anyway....

As fixitron mentioned, flux is the stuff that basically "wets" the joint so the solder sticks to it. Rosin core solder is used in the electronics field because it is much less corrosive than acid core solder, and because it's non-conductive. There are different types of rosin flux, but most of them can be left on sensitive electronic assemblies without hurting them, for years. Acid core solder would wreck them. Acid core solder is used for plumbing because it "fluxes" better, and because it's water soluble. It may be more corrosive than rosin core, but not enough to hurt copper or brass. The water flowing through the lines carries away any flux on the inside of the joint, and carries it away.

So if you use rosin core solder on plumbing, you may have little bits of rosin flowing through your pipes, which water won't dissolve. Probably not good for a hot water heating system. Probably not good for any plumbing system. Because rosin flux isn't as aggressive as acid flux, you'd be less likely to have a good joint. Also, if you use acid core solder on electronic stuff, and don't wash it off very well and right away with water, you'll wreck it.

Oh yeah, and the other difference is that rosin core solder is usually 60/40 or 63/37, which melts at a bit lower temp than 50/50 plumbing solder. The lower heat is nicer for the little parts.

Tom

 

Tom,
Welcome to the board & thanks for the insight on rosin core solder. In the heating trade we use solid solder with separate flux. For heat loops it is OK to use 50/50 but for domestic you must use lead free solders. The lead free solders have a higher melting point but are stronger. Just to prevent any possible mistakes I don't even carry lead bearing solder on the truck.

 

That's a good idea. For me it will be "little tool box", rather than truck, but it'll avoid mixing things up. (The rosin core I have is 22 gauge and 28 gauge...even if I'm sleepy I won't confuse that with the big stuff.)

I had hot water heat as a kid, then spent 20+ years renting and putting up with forced air. Now, I've bought a house with hot water, and I'm a happy camper. I'm planning on popping in with questions later, for now I'm reading up and learning.

The part that gets me the most, though, is you guys. People come on here, with a heating problem, cold and scared. You guys talk to them, calm them down, and head them in the right direction. Kind of like in the old movies where the guy in the control tower talks down a pilot that freaks out. It's a pretty neat thing. Thank you for all the info!

 

all of the control tower scenes from Airplane! with Lloyd Bridges and Robert Stack just flashed through my head. LOL.

 

I used rosin core on my boiler for all of the joints on the closed-loop side. Most important thing is cleaning the copper. I also fluxed the joints before I sweated them. I like the way the old lead solders flow compared to the newer no lead stuff. Also, have a ton of the rosin core stuff laying around. There's also a very wide variety of rosin fluxes out there, some are more aggressive than others (activated).

Pete

 

Boy this one goes way back. Ill go back farther.
To solder yes you try and clean the metal or copper as best as you can . Then comes the flux to clean it more so the solder will go to the metal.. For the Gal. sheet metal you use mutactic
acid. For copper sheets you use a cut acid. To make that you put zinc into the muractic acid till it dont cook anymore. Then thats your copper flux. Now Rosin that you buy by the lb. To use on a turnplate roof. Or metal roof when you did a metal deck like you put that down in 2'X2' sq. Then came back and sprinkle rosin down all the seams so you could solder them. The rosin would melt as your flux and the solder would flow right into a seam. So as with electronice now and no acid that would leave the new metal roof all solder up with no acid to clean up. Oh and you use a 8 lb hatchet iron to solder the roof
Boy it sure helps to have all this done for us now Right in the solder. They have a flux out that they say you dont have to clean the copper water pipe just put the flux on and add solder with heat. Then we have a flux paste put it on the copper and add heat thats all. I can recall when you had to tin the copper pipe and fittings first then put them together and sweat them in.
Oh and we used a charcoal pot for the sloder irons

ED My .02 cents

 

And I thought I was the resident old goat. Did you have to make your own charcoal? LOL

 

Grady How far back do you go? I can recall look ing at a home as you walked to it and knew if it took a 18",20", or a 24" furnace. You didnt have wall to wall carpet. So if a room had a 10X10 rug it got a 10X10 register. Big room rug was say 12'X14' it got a 12"X 14"register. Code called for all outside cold air intake so that was like 24" round to the outside. After the home got CO you closed the cold air pipe from outside and took it all from the basement. This was all had fired
Oh well fun fun
ED

 

Not quite that far. I will admit to sizing A/C based on square footage (as strided off) but that was more than a few years ago.